In recent years, attentions have been drawn to the USB (Universal Serial Bus) as an interface standard for connection between a personal computer and peripheral units (broadly, electronic instruments). The USB has a merit that connection by the connector of the same standard can be made with peripheral units, such as a mouse, a keyboard and a printer, that conventionally have required connection by the connectors of different standards, and further so-called plug-&-play or hot-plug is possible to realize.
Meanwhile, the USB has a drawback to low transfer speed as compared to that of the IEEE1394 in the spotlight as also the serial bus interface standard.
In such circumstance, the USB2.0 Standard has been plotted and highlighted to attain a data transfer rate of 480 Mbps (HS mode) by far higher compared to that of the USB1.1 while possessing lower compatibility with the conventional USB1.1 Standard. Furthermore, the UTMI (USB2.0 Transceiver Macrocell Interface) have been plotted to define the interface specifications on the USB2.0 physical-layer and logical-layer circuits.